Introduction Short messaging service (SMS), or text messaging is highly accepted in medical education of health workers and patients. This study was conducted to evaluate if SMS-based supplementation of key messages with conventional classroom teaching compared to conventional teaching results in a better cognitive performance of undergraduate medical students. Materials and Methods Setting: Department of pediatrics of a public medical college in India. Participants: Ninety-two final-year undergraduate medical students. Study design: Single-center, nonrandomized, controlled trial. Intervention: One batch was given SMS-based key messages in addition to conventional teaching (intervention group, n = 48), as compared to only conventional teaching of the other (control, n = 44) batch. The text messages pertained to five predetermined topics of the teaching session and were sent in the evening of the day the topic was taught. Primary outcome variable: Scores in a multiple-choice question (MCQ)-based test at the end of posting of each batch. Results A total of 92 final-year MBBS students were enrolled in the study. There was no statistically significant difference between the performance of the study participants in the post-intervention MCQ test in the two groups [mean (standard deviation) scores, 13.4 (1.55) vs. 9.7 (3.49), P > 0.05], even after subgroup analysis for high scorers and low scorers. The total cost of sending the messages was less than Rs. 100. Conclusion There was no statistically significant effect on cognitive performance following a supplementation of classroom teaching by SMS-based key messages. However, given the low cost of this methodology and the reported high acceptance of this method by students, there is a need for more well-planned studies to confirm these results.